Metal pipe of a both corrugated and spiral rib design is widely used for drainage, culverts, and other similar fluid conduits. Although susceptible to abrasion and corrosion, metal (e.g., steel) pipe has advantages over concrete pipe and the like due to its comparatively high strength and low weight. These characteristic render metal pipe relatively inexpensive to manufacture, ship, and handle, while permitting its use in applications requiring it to support substantial soil overburden. Applicant has previously introduced a particular spiral ribbed steel pipe into the marketplace having a hydraulic efficiency comparable to more costly concrete pipe and possessing superior structural capabilities for prolonged use in buried storm drain applications.
Since metal pipe is susceptible to corrosion and excessive abrasion, it use has previously been restricted primarily to culvert and storm drain applications. In sanitary applications (e.g., sewer systems), corrosion causing sulfuric acid is formed from hydrogen sulfide gas generated by waste products. Such waste products and/or acid has rendered the use of metal pipe in sanitary applications impractical since it rapidly deteriorates in the corrosive environment. As such, much heavier and more expensive concrete, lined concrete, and/or vitreous clay pipe has traditionally been utilized for sanitary applications. Thus, although metal pipe is generally preferred because of its high strength and comparatively low weight and cost, it has heretofore not been widely used in sanitary applications due to its susceptibility to corrosion.
Though often used in storm drain applications, metal pipe is nonetheless susceptible to extensive abrasion caused by the movement of gravel, dirt, sand, etc. therethrough. Such excessive abrasion frequently degrades the metal pipe to a point where leakage therefrom becomes a major concern. Additionally, such abrasion may, in some instances, be sufficient to adversely affect the structural integrity of the pipe, and consequently result in the structural failure thereof when the soil overburden crushes a portion of the pipe, thereby effectively plugging the pipe and substantially reducing or eliminating flow therethrough.
In recognition of the advantages attendant to the use of metal pipe, Applicant has also developed and introduced into the marketplace a spiral ribbed metal pipe which is provided with an integrally formed polymer liner, thus allowing for the use of the metal pipe in relation to sanitary or sewer applications. The liner of this metal pipe of the Applicant is adapted to withstand the corrosive environment found in sanitary applications, as well as the abrasive environment found in storm drain applications. In addition to being provided with the corrosion/abrasion resistant liner, this metal pipe of the Applicant is also provided with an outer coating to protect the exterior thereof from the corrosive effects of long-term exposure to the burial environment. This metal pipe of the Applicant is more fully described in its U.S. Pat. No. 5,316,606 entitled METAL PIPE WITH INTEGRALLY FORMED LINER AND METHOD OF FABRICATING THE SAME issued May 31, 1994 and U.S. Pat. No. 5,480,505 entitled METHOD OF FABRICATING A STEEL PIPE WITH INTEGRALLY FORMED LINER issued Jan. 2, 1996, and U.S. application Ser. No. 08/504,774 entitled STEEL PIPE WITH INTEGRALLY FORMED LINER AND METHOD OF FABRICATING THE SAME filed Jul. 20, 1995 and application Ser. No. 08/866,812 entitled STEEL PIPE WITH INTEGRALLY FORMED LINER AND METHOD OF FABRICATING THE SAME filed May 30, 1997. The contents of the aforementioned pending applications and issued patents are incorporated herein by reference.
Though Applicant's lined metal pipe overcomes the problems associated with corrosive or abrasive degradation when such pipe is used in sanitary or storm drain applications, problems are still encountered at the joints between adjacent sections of such pipe, particularly when used in sanitary applications. In this respect, when sections of the lined pipe are joined to each other in end-to-end fashion, the contact between the lining of the pipe sections is sometimes not fluid-tight, thus giving rise to the leakage of corrosive fluid therebetween. The lack of a fluid-tight seal between the pipe linings is often attributable to irregularities or flaws within those lined surfaces which are abutted against each other to form the joint. Also contributing to the difficulty in creating a fluid-tight seal between the pipe linings is the fact that the pipe walls to which the linings are integrally connected are often not perfectly round, thus causing the linings applied thereto to be out of round as well. As will be recognized, when one or both of the lining ends abutted against each other to form the joint are out of round, there is a greater susceptibility for occurrences of leakage therebetween. Moreover, the irregularities defined in the ends of the adjacent pipe sections attributable to the inclusion of the outwardly protruding spiral ribs gives rise to further difficulties in forming a fluid-tight joint therebetween.
The leakage of the corrosive fluids between the polymer pipe linings typically results in the exposure of the metal pipe walls adjacent the joints to such corrosive fluids and the resultant corrosion or degradation thereof. The corrosion of the metal pipe wall about the joint attributable to its exposure to the corrosive fluids causes a weakening of the joint which results in its eventual failure. The failure of the joint in turn results in large quantities of leakage of the corrosive fluids from within the conduit defined by the connected pipe sections.
As such, there exists a need in the art to provide pipe adapted for use in corrosive or abrasive environments with cuffs for use in forming leakage resistant joints between adjacent sections of the pipe. The present invention specifically addresses this need in the art.